A do-it-yourself approach to Web software called Ajax has led to a new breed of fast, highly interactive sites and includes Google and Yahoo developers among its adherents. Now large technology vendors that rely on keeping software developers in their fold are either downplaying the trend--or in Microsoft's case, trying to capitalize on it.

Microsoft said late Monday it's developing a tool code-named Atlas that programmers will use to quickly write fast-loading Web sites that employ code running in a Web browser.

Examples of this approach using Ajax are Google Maps and Yahoo's Flickr photo-sharing site, which are written using a home brew of JavaScript, Dynamic HTML, and XML. Ajax stands for "Asynchronous JavaScript plus XML." Sites that employ it can update their contents in the background while a user is at the site, then have new text or graphics ready to load in an instant, instead of waiting for pages to reload.

Ajax sites don't rely on special media players, since the underlying technologies work with nearly all Web browsers. The result is applications like Google's maps site, which lets users zoom and scroll around a map of North America with uncommon speed for the Web.

"There are a lot of people using Ajax," says Mike Gilpin, an analyst at Forrester Research. While Ajax apps don't have the interactivity of software written with Microsoft's Windows technologies, Macromedia's Flash player, or the open-source Eclipse tools for Java, Ajax doesn't require developers to download a set of tools or media players from any one software vendor. That's attractive to some savvy programmers, but makes Ajax programming labor intensive. "Not everyone can justify the amount of effort it takes to create that kind of user interface," says Gilpin. "Not everyone is Google."

That's where Microsoft hopes to change things. At its Professional Developers Conference Sept. 13-16 in Los Angeles, the company plans to release a "developer preview" test version of Atlas for Ajax-style development on Windows. Atlas will contain JavaScript code that works with Microsoft's Visual Studio 2005 development environment, due in November, and its ASP.Net 2.0 technology for writing Web apps. Using Atlas, developers will be able to write Ajax apps that contain pre-written code to smooth over technical distinctions between Web browsers, and debug those apps with Microsoft-branded tools, says Charles Fitzgerald, a general manager at Microsoft. Using Ajax today, he says, "is a little bit of a hack."

To be sure, Microsoft and other software companies have shipped products that use Dynamic HTML, JavaScript, and XML for years. For example, the Web client for Microsoft's popular Outlook E-mail software uses those technologies to speed up interaction. But vendors are paying more attention to alternatives to their development tools amid renewed interest by customers in easy-to-use software. The trend has been propelled in part by a spate of new features from Google, Yahoo, and Microsoft's MSN site and the desire for companies to stand out online, Fitzgerald says. "There's a battle for customer attention," he says.

Microsoft isn't the only tech company that views Ajax development as a potential threat. If programmers choose do-it-yourself alternatives to commercial tools from companies such as Macromedia and Sun Microsystems, it could decrease the chance that they'll license other software from them. In an interview earlier this month, Kevin Lynch, executive VP and chief software architect at Macromedia, said writing Ajax apps requires repetitive testing to iron out bugs caused by different browsers, and pointed to a lack of commercial tools. "With Flash, you build once and use the same run time," he said.

James Gosling, a VP and fellow at Sun Microsystems and inventor of the Java computer language, said recently that while many developers use Ajax and Java in conjunction, Java is a more productive programming environment. "Ajax is really good for whizzy looking Web pages," he said. "Google impressed a lot of people with their maps site. What they don't tell people is the amazing amount of pain they went through in trying to make that work on other platforms."